Synthesis of covalent organic framework with amino affinity groups for enhanced selective adsorption of diclofenac sodium from aqueous solution

Abstract

The presence of diclofenac sodium (DCF) is widespread in environmental waters, leading to issues for ecosystems and human health. Hence, the removal of DCF from aquatic environments is crucial. This study innovatively designed and proposed an urchin-like covalent organic framework (COFs) with affinity groups to enhance its selective adsorption capacity for DCF. As a proof-of-concept, an amine-functionalized COF (TAPT-DVA-NH2) was synthesized via the thiol-ene click reaction between vinyl-COF (TAPT-DVA) and cysteamine for the purpose of adsorbing DCF from water. The adsorption kinetics, isotherms, the influences of pH, ionic strength, and regeneration of TAPT-DVA-NH2 for DCF were investigated thoroughly. The synthesized COF TAPT-DVA-NH2 exhibited exceptionally rapid and efficient DCF capture. The rate constant k2 was 0.0196 g/mg/min, and the maximum adsorption capacity could reach approximately 398.4 mg/g. The exceptional adsorption performance of COF TAPT-DVA-NH2 was attributed to electrostatic, π-π, hydrophobic and hydrogen bond interactions. The adsorption efficiency of DCF on COF TAPT-DVA-NH2 remained above 95 % even after five regeneration cycles. In addition, the self-made adsorbent efficiently adsorbed DCF from real environmental water samples. Thus, this highly efficient and recyclable adsorbent holds significant potential for DCF removal from aquatic environments.